1. Field of the Invention
The present invention relates generally to an apparatus for preparing a drainage trench, such as a trench positioned adjacent to the side of a roadway to drain water from the road subbase. More specifically, the invention relates to a drain preparation apparatus which performs at least the following steps in a single pass: lining the bottom and a single side wall of the trench with a filter fabric, pouring a first layer of bulk material on the filter material, laying a drainage pipe on the first layer of bulk material and pouring a second layer of bulk material on the drainage pipe to cover the pipe and fill the trench.
2. Description of the Prior Art
It is customary practice among civil engineers and road construction experts today to provide drains along roadways to allow for proper drainage of water from road subbases to thereby avoid subbase failure and to prolong the life of road pavement. Typically, such drains are constructed by first digging a trench parallel to the edge of the roadway using a conventional trench digging machine, backhoe or the like.
To prepare the drain, the trench must first be lined with a suitable filter fabric to provide a permeable barrier between the bottom and sides of the trench and the drain pipe. Such a permeable structure prevents the flow of silt or the like into the drain pipe. After the filter fabric is laid, a first layer of bulk granular material, such as draincrete, gravel or the like, is poured into the bottom of the trench. A pipe through which the water may drain is then laid on top of the first layer of bulk material, after which a second layer of bulk material is poured to cover the pipe and to fill the trench.
The preparation of a drain from a bare trench is thus a multi-step process, involving the sequential performance of various tasks which can only be performed after previous steps have been completed. As a result, the drain preparation process is very time consuming and therefore expensive. In addition to being time consuming, the process has also historically required the use of different apparatus to perform the different steps, adding further to the complexity, labor and cost of the process.
Prior art apparatus for performing more than one of the various steps necessary to prepare a trench for use as a drain have been attempted in the past. For example, U.S. Pat. No. 4,289,424 to Shefbuch, et al. discloses an apparatus for laying a drain conduit in a trench, together with embedment material. The Shefbuch, et al. apparatus includes a hopper with a drain pipe chute 45 running through it. The discharge end of chute 45 protrudes through a bottom rear opening in the hopper so that pipe and gravel are simultaneously laid in the trench bottom as the apparatus is towed by a conventional trenching machine.
U.S. Pat. No. 4,806,043 to Fournier discloses a machine for lining a trench with filter cloth 14, laying down a drain pipe 15 directly on filter cloth 55, filling the trench with gravel 34, and then sealing the top edges of filter cloth 14 together to encase the drain pipe and gravel.
U.S. Pat. No. 4,812,078 to Rivard discloses a machine for simultaneously laying a conduit such as a telephone cable 6 and sand 41 (which surrounds the conduit) in a trench, laying a marker film 55 on top of the sand, and then back-filling the trench using plowshares 61 and 61A.
U.S. Pat. No. 4,832,531 to Paulovits discloses an apparatus for simultaneously laying irrigation pipe and a strip of water-impervious plastic film (underneath the pipe) in a small trench about 60 centimeters deep. The apparatus includes a splitting tool to provide a slit in the ground and a wing type hollow head for widening the slit underground. The plastic film is fed to the hollow head in folded form and is unfolded by guiding means associated with the head before it is laid on the bottom of the subterranean trench.
U.S. Pat. No. 5,174,685 to Buchanan purports to improve over the Shefbuch, et al. '424 patent and discloses tapering the hopper from rear to front. Because of the taper, it is alleged that only the rear corners of the hopper engage the side walls of the trench, thus creating minimal frictional resistance.
While the prior art, as exemplified by the patents discussed above, has attempted to provide apparatus capable of performing multiple drain preparation steps in a single pass, each of the apparatus discussed above has various disadvantages which make them less than satisfactory for prolonged commercial use. For example, no means are disclosed in Fournier for pouring a first layer of bulk material before laying the drainage pipe in the trench. In addition, in Fournier, filter material 14 is laid in the trench by pressure from drainage pipe 15. As a result, filter material 14 will not seat tightly and evenly along the sides and bottom of the trench.
Still further, Fournier teaches laying filter material on all three sides of the trench, that is, on both vertical walls and the bottom of the trench. In practice today, however, some State Highway Departments, such as South Carolina, require that the trench be lined only on the bottom and on the side wall farthest from the road. This construction is mandated by the South Carolina Highway Department to increase the flow of water from underneath the road surface into the drain. The Fournier apparatus cannot meet this requirement.
Shefbuch, et al. provides means for pouring bulk material into a trench but does so simultaneously with the laying of pipe 15. As a result, irregularities can result in the positioning of pipe 15 and in the amount of bulk material which is poured above and below the pipe, thus reducing the effectiveness of the draining operation. In addition, the Shefbuch,.et al. apparatus discloses no means for laying a filter material in the trench.
Buchanan suffers from the same limitations as Shefbuch, et al.
Accordingly, it is an object of the present invention to provide a drain preparation apparatus for performing in a single pass at least the steps of lining a trench with a filter material, laying a first layer of bulk material on the filter material, laying a drainage pipe on the first layer of bulk material and laying a second layer of bulk material on the drainage pipe to cover the pipe and fill the trench.
It is a further object of the present invention to provide a drain preparation apparatus wherein the flow of the second layer of bulk material may be controlled to enable the drain preparation apparatus to satisfactorily prepare lateral drains.
It is yet a further object of the present invention to provide an improved apparatus for guiding and folding the filter material and laying the folded filter material on the bottom and only one side wall of the trench.
It is a still further object of the present invention to provide a soil recovery apparatus adapted to be used with a conventional trenching machine, the soil recovery apparatus recovering soil dislodged by the trenching machine so that the resulting trench is substantially free from berms of soil created adjacent the sides of the trench.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements, combinations and methods particularly pointed out in the appended claims.